The former seat of royal government was Egreth in the Westlands but Dimwit's love of the Eastlands has always been given as the main motive behind the capital's relocation and the small village Aragain, in a surprisingly short amount of time, was transformed and renamed, quickly becoming the center of civilization as it was then known.
At its peak, the castle at Flatheadia housed 90% of the Empire's population.Much like Egreth, its counterpart in the Westlands, Flatheadia was the focus of all new underground tunneling and exploring in the area.
The population of Flatheadia steadily declined after Dimwit's death in 789 GUE, due to fears of the Curse of Megaboz. These fears became reality when, in 883, the Curse that had been postponed 94 years succeeded in destroying the Empire, and Flatheadia along with it.
All that remains of Flatheadia today is a simple White House.
The Flatheadia Village-turned-metropolis was inside the wall, and its entrance was marked by two gnarled elms, leading to a Shady Park, a mall featuring a large elm. The Underground Revenue Service was on the north and the Church of Brogmoidism to the south. Eastwards, was the Post Office and the Courtroom. The dominating feature of the Flatheadia landscape after 781 GUE was the 400-story FrobozzCo HQ, designed by Frank Lloyd Flathead.
The immersive Flatheadia Castle was encircled by a moat, passed by a Causeway, a peninsula of dirt and gravel. The drawbridge was opened and closed by the guards in a Barbican. Outside the drawbridge, there was the Outer Bailey with an ancient mighty elm and a treasure chest buried nearby.
The West Wing accessed through a locked door opening with a steel key, has a more recent styling: smoothly dressed stone inlaid with marble patterns. A faint small of fudge hanged in the air. On the north was a Peg Room with a Peggleboz board. Once the First Dungeon Master beat it, a door opened to a Game Room with the sole 100000 zorkmid bill of J. Pierpont Flathead. On the south was the Gym, obviously added by Dimwit's successors.
Westwards, it leads to the Hangar with a dirigible to Fenshire.
The East Wing was accessed through a hall door, opened with an iron key that was found in Dimwit's Solar. It contained a Library which contained a copy of Encyclopedia Frobozzica and T.J. "Stonewall" Flathead's lance, the biggest Chapel of all Quendor with access to the Crypt below
There was also a Guest Room, the Servants Quarters and the Jester's Quarters which contained a Tower of Bozbar game which opened 3 secret rooms. The northern one contained goggles and a crate of red clown noses, the western one a cup of magic potion that gave the ability to listen to plants, and the eastern contained the manuscript of On the Discoloration of Roadside Slush.
The Secret Wing is to the south of the Flatheadia castle. It was accessed behind Dimwit's throne, whenever he snapped his fingers.
The Lower underground Levels of the castle, dominated by the Lower Hall, under the Great Hall of the Castle, had several sections like the Thomas Alva Flathead's Froblo Park, the Royal Zoo, Hellhound Kennels. Eastwards it leads to the Lake Flathead, and westwards it leads to the Great Underground Highway.
A Lowest Hall led to a section with a Vault, a Storeroom with magical passages for the Rockville Estates and lower than that, bottomless Pits. The First Dungeon Master filled the pit with an anti-pit bomb in order to take Thomas Alva's lantern, descended some caves and then a Well until Under the World and saw the Great Brogmoid.